my dh is from india and we took our now 3 1/2 ds to india last january to new delhi when he was 2 1/2. He is partially vaxed. (he got all vaxes up until 6 months, when we decided to stop vaxing him completely). We didn't take any precautions for any diseases, other than bringing deet spray. Ds did get bit by one mosquito, but nothing became of it. We did go in the colder season which there are way less mosquitos, but still plenty flying about. When we returned to the states we did end up taking him to urgent care because of a fever, which turned out to be an ear infection from virus he had, which made him very conjested, but the doctor didn't seemed concerned about the mosquito bite. I did a bit of research on malaria when ds got the bite and from what i read the more deadly strain is found in sahara in africa, but malaria can lay dorment for years...I would just bring lots of deet spray and spray it on the bedding, clothes and keep as much body covered as possible. Those mosquitos are very thirsty though, as my ds was always wearing long sleeves and he got bit on the neck...Also remember mosquitos like to come out in the dawn and dusk hours, so try to stay indoors with the windows shut at those times. HTH, and good luck on your trip!
Also from reading up on the malaria meds, they are the same they give both before and after infection, so just keep that in mind. I would probably pass on them if i were you, but talk it over with your dh and decide together what you feel is best for your family.
since last january was my first trip to india, i got a lot of good advice from this website:
http://www.indiamike.com/india/ you may want to check that out for some answers to your questions...